The present invention relates to a robot control method and apparatus.
It is typical in the prior art to use an offline robot, that is, a robot which is at a place different from the place at which actual work is to take place, for the purpose of teaching an online robot. A workpiece is fixed to a fixed position, and a workend of that offline robot is aligned with three or more reference points on the workpiece, and those reference points are stored along with each of a plural number of positions where the work is to be carried out. Work of this type can be painting the bodies of automobiles, for example. Then, an online robot, that is, a robot installed at the position where the actual work is to take place is used for teaching three or more reference points on the workpiece at predetermined stop positions for the performance of the work itself. Then coordinate transform matrices are created for transforming from the offline coordinate position to the online coordinate position, and these coordinate transform matrices are used to transform the teaching data made when offline into teaching data of the online robot.
With this prior art, it is necessary to accurately set the relative positions of the workpiece and each robot both for offline and online measurement, and the teaching involves much trouble if there is a discrepancy in the relative positions of the workpiece and each robot. In addition, when a work is operated upon by a robot, the supplied workpiece must be stopped at a position which is accurate relative to the position of the online robot. If this is not the case, then it will be difficult to perform accurate work.
With other prior art technologies, a matrix PW for the relative positions on the workpiece of the work coordinates is created when teaching of an offline robot is performed and a matrix PR for a position on the robot coordinate system of the workpiece is created in the status where a workpiece is accurately stopped at a predetermined position relative to the position of the offline robot. The matrix PW and the matrix PR are used to calculate the position P on the robot coordinate system of the workend which is to be held by the robot.
However, with such prior art, each of the positions P where the workends of each robot are to operate cannot be actually known unless there is calculation of the product PW.PR. Accordingly, with this prior art, there is the problem that it is not possible to use comparison with the operable range of the robot and to perform teaching while confirming whether the robot is within the operation range, and there is thus the problem that it is not possible to have direct sensory knowledge of the position P of the workend of the robot.
Also, with this prior art, in addition to the matrix PW for the relative position of the workpiece on the work coordinate system, it is also necessary to set data for the shape of the workend of the robot, that is, information for whether the articulated joints of the robot move to the left or right, and for the number of rotations of the articulated joints. Because of this, there is also the problem that the amount of data which has to be stored becomes excessive.
Examples of this prior art are Japanese patent Laid-Open Application No. 269205-1987, No. 8906-1988, No. 253405-1988 and No. 302405-1989.